Field code
issue?.links[0]?.outwardIssue?.key

Links are stored in lists. Documentation on how to work with lists can be found here.

You can access the whole link by issue?.links[0].outwardIssue which returns an Issue object, issue?.links will return a list of objects.

Read

Returned valueThe outward issue key of the first link. If no link is available, null is returned.
Output data type

TEXT

Example outputPRJ-77

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